Technical Field
The present disclosure relates to a control device for a vehicle, and particularly to a control device for a vehicle equipped with an internal combustion engine including a fuel injection valve.
Description of the Background Art
Japanese Patent Laying-Open No. 2012-097640 discloses a fuel supply device including a residual pressure holding valve that is disposed downstream a fuel feed pump to hold the pressure in a pipe for supplying a fuel to a fuel injection valve of an engine at a prescribed pressure during stoppage of the feed pump.
When the operation of the engine is stopped and the fuel feed pump is stopped, the residual pressure holding valve is closed to prevent the pressure in the fuel pipe from decreasing. When the residual pressure holding valve is closed, the fuel that has been discharged from the fuel pipe via the residual pressure holding valve to a fuel tank is stopped being discharged, and the pressure in the fuel pipe is maintained at the prescribed pressure.
In recent years, for improved fuel efficiency, an engine system configured to cause the fuel feed pump to operate in accordance with the state of an engine load has been considered. In such an engine system, an ECU sets a target pressure of the fuel to be supplied to the fuel injection valve (hereinafter, the pressure of the fuel may be referred to as the “fuel pressure”, and the target pressure of the fuel as the “target fuel pressure”), and the fuel feed pump is operated to achieve the target fuel pressure.
In this engine system, when the target fuel pressure is reduced and the rotation of the fuel feed pump is set low, the residual pressure holding valve is closed to prevent the pressure in the fuel pipe from decreasing. When the residual pressure holding valve is closed, the fuel that has been discharged from the fuel pipe via the residual pressure holding valve to the fuel tank is stopped being discharged, and the pressure in the fuel pipe increases above a valve opening pressure of the residual pressure holding valve, which causes the residual pressure holding valve to open. This causes the pressure in the fuel pipe to decrease below the valve opening pressure of the residual pressure holding valve, which causes the residual pressure holding valve to close again. The residual pressure holding valve assumes only the two positions, i.e., open and closed positions, and does not assume a position such as a half-open position. Thus, if the pressure in the fuel pipe where the residual pressure holding valve is disposed remains around the valve opening pressure for a long time, the residual pressure holding valve is repeatedly opened and closed.
The repeated opening and closing of the residual pressure holding valve (with chattering being generated) is undesired in that this opening/closing noise may sound unpleasant to a passenger.